1. Field of the Invention
The present invention relates to an exhaust system for a vehicular two-cylinder engine and, more particularly, to an exhaust system suitable for an automotive two-cylinder v-engine mounted on a straddle-type all-terrain vehicle.
2. Description of the Related Art
Conventional exhaust systems for a vehicular two-cylinder engine are classified into those provided with a single muffler for two cylinders and those provided with two mufflers respectively for two cylinders. FIG. 7 is an exploded perspective view of a conventional exhaust system for a two-cylinder V-engine mounted on a motorcycle. This exhaust system is provided with a single muffler 105. The exhaust system includes a front-cylinder exhaust pipe 100, a rear-cylinder exhaust pipe 101, a collecting pipe 102 having an outlet 103, and the muffler 105 provided with a connecting pipe 106. The outlet 103 of the collecting pipe 102 is connected to the connecting pipe 106 of the muffler 105. The front-cylinder exhaust pipe 100 is extended rearward under the crankcase of the two-cylinder engine and is connected to the connecting pipe 106 of the muffler 105 disposed behind the two-cylinder engine via collecting pipe 102.
An exhaust system including two mufflers respectively for the two cylinders of a two-cylinder engine has two exhaust pipes each having one end connected to the cylinder and the other end connected to the muffler.
The exhaust system shown in FIG. 7 needs the collecting pipe 102 of complicated construction, many connecting parts for connecting the exhaust pipes 100 and 101 to the collecting pipe 102, complicated piping and troublesome assembling work.
The exhaust system provided with the two mufflers for two cylinders needs spaces for the two mufflers.
When a two-cylinder V-engine is mounted on a saddle-type all-terrain vehicle, and the front-cylinder exhaust pipe is extended rearward under the crankcase, the exhaust pipe is close to the surface of the ground. Therefore, the exhaust pipe is easily covered and dirtied with mud and sand. The pipes must be arranged in a compact piping securing a sufficient road clearance, i.e., clearance between the front-cylinder exhaust pipe and the surface of the ground, to avoid the front-cylinder exhaust pipe striking against stones and rocks.
Accordingly, it is an object of the present invention to provide an exhaust system for an automotive two-cylinder engine, consisting of a relatively small number of parts and facilitating work for mounting the exhaust system on a vehicle.
Another object of the present invention to provide an exhaust system for a two-cylinder V-engine mounted on an all-terrain vehicle, including exhaust pipes and a muffler, which the exhaust pipes are extended so that a space around the cylinders of the two-cylinder V-engine may be effectively utilized, the all-terrain vehicle may have a relatively small overall width and the exhaust pipes may not be dirtied with mud and sand and may not strike against stones and rocks.
According to a first aspect of the present invention, an exhaust system for a vehicular two-cylinder engine having a first cylinder and a second cylinder includes a single muffler provided with two connecting openings, a first-cylinder exhaust pipe having one end connected to the first cylinder and the other end connected to one of the connecting openings of the muffler, and a second-cylinder exhaust pipe having one end connected to the second cylinder and the other end connected to the other connecting opening of the muffler, wherein at least either the first-cylinder or the second-cylinder exhaust pipe is connected detachably to the connecting opening of the muffler. Thus the exhaust system does not need the collecting pipe having complicated construction, the exhaust pipes can be extended in a simple arrangement, and the exhaust system facilitates assembling work.
Preferably, in the exhaust system in the first aspect of the present invention, the first muffler is a front cylinder disposed at a front portion with respect to a moving direction of a vehicle, the second muffler is a rear cylinder disposed at a rear portion with respect to the moving direction of the vehicle, the second-cylinder exhaust pipe is connected to the connecting opening and is welded to the muffler, and the first-cylinder exhaust pipe is connected detachably to the connecting opening. Connection of the second-cylinder exhaust pipe connected to the rear cylinder nearer to the muffler by welding further facilitates assembling work.
According to a second aspect of the present invention, an exhaust system for a two-cylinder V-engine having a front cylinder and a rear cylinder and mounted on a saddle-type all-terrain vehicle, said exhaust system includes a muffler disposed behind the two-cylinder V-engine, a front-cylinder exhaust pipe having one end connected to a front cylinder, the front cylinder being disposed at a front portion with respect to a moving direction of a vehicle, and a rear-cylinder exhaust pipe having one end connected to a rear cylinder, the rear cylinder being disposed at a rear portion with respect to the moving direction of the vehicle, wherein the front-cylinder exhaust pipe is bent so as to extend rearward along side surfaces of the front and the rear cylinder to the muffler. Thus the long front-cylinder exhaust pipe of the exhaust system can be extended through a dead space around the side surfaces of the front and the rear cylinders so that the same may not protrude laterally and hence the exhaust system has compact construction.
Preferably, in the exhaust system in the second aspect of the present invention, the muffler is provided with two connecting openings, the rear-cylinder exhaust pipe is connected to one of the connecting opening and is welded to the muffler, and the front-cylinder exhaust pipe is connected detachably to the connecting opening. Connection of the rear-cylinder exhaust pipe connected to the rear cylinder nearer to the muffler by welding further facilitates assembling work.